Multi-story buildings include at least one floor located above another. A fire that starts on a lower floor will transfer heat to the floor above. With proper design, the floor construction will allow adequate time for people on the upper floor to vacate the building. The inherent thermal characteristics of concrete are considered during the design phase. At a given thickness, concrete will retard the transfer of heat for a set time. A reduction of the thickness of the concrete will potentially compromise the floor design and reduce the time occupants have to escape from a fire. Likewise, any opening or through-penetration of the floor will permit the heat and/or fire to travel between the floors.
Buildings often require a reduction of concrete thickness or penetration through the floor for functional purposes. Common examples include plumbing fixtures, HVAC ductwork, and electrical conduits and outlet boxes. Products such as electrical outlet boxes, when embedded in a concrete floor, reduce the floor's insulation capacity. A common method for restoring insulation capacity is to apply a sprayed insulation under the floor directly below the outlet box. Another method to insulate the outlet box is to construct a wallboard enclosure that is secured below the floor directly below the outlet box. These common methods for increasing insulation capacity have positive effect only when the below-floor insulation is properly aligned with the above-floor outlet box.
Additionally, an electrical conduit must be attached to the outlet box for distribution of electrical services. Typically, the conduit is routed through the concrete between the outlet box and a nearby utility distribution room. Through-deck routing further compromises the thermal performance of the floor, since the embedded conduit displaces the concrete. Alternatively, the conduit is routed from the outlet box directly below the floor. The below-floor routing does not directly compromise the thermal performance of the floor. However, the below-floor conduit provides a passageway from below the floor into the outlet box. Without sealing this passageway, heat and flame generated by a fire below the outlet box can travel through the conduit, accelerating the transfer of heat to the outlet box.
Therefore, there is a need to provide an improved fire classified floor box assembly.